Basically, today's optical touch system employs two image sensing devices for the touch sensing; wherein the imaging sensing device is configured to sense images on a touch surface of the optical touch system. Specifically, the optical touch system is configured to, when an indicator object closing to the touch surface is detected, determine the position of the indicator object relative to the touch surface according to the indicator object image (i.e., the light-blocking point) in the images captured by the image sensing device.
However, if there are two indicator objects on the touch surface and the two indicator objects are positioned within a specific distance or within a specific view angle from the image sensing device, and thereby resulting in one indicator object image blocking another indicator object image in the image captured by the image sensing device, the optical touch system may not correctly determine that there are two individual indicator objects on the touch surface due to the two indicator object images are merged to each other.